You may not think of a chipmunk as a pest, but when it starts digging under shrubs or patios, your view may change. Chipmunks actually cause the costliest damage to established landscapes, unseating retaining walls, destabilizing walkways and even killing mature roses or shrubs (by digging directly under the trunk). Once chipmunks dig tunnels, other critters arrive to set up housekeeping in those tunnels, including voles, shrews and snakes. Chipmunks visit gardens with bird feeders and other ready sources of food or water. An outdoor cat or dog can help keep these critters at bay, as can garlic oil pegs you toss into tunnels or various repellents you sprinkle onto flower beds or near tunnel openings.